Laser protective eyewear having improved glare protection

ABSTRACT

A molded optical filter is provided having effective filtering of energy emissions at an optical density (OD) of greater than 4 in three energy emission bands corresponding to the wavelengths of laser emissions while preserving the wearer&#39;s ability to differentiate and recognize colors and having a pleasing overall color. The selective optical filter is a moldable polymer filter that has three dyes therein to produce sharp notch filtering ranges at about 530 nm, 700 nm and 1060 nm and a fourth color balance dye therein to adjust the overall color of the filter making it more pleasing and desirable to the wearer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of earlier filed U.S. patentapplication Ser. No. 12/108,557, filed Apr. 24, 2008.

BACKGROUND OF THE INVENTION

The present invention relates generally to optical safety filters. Morespecifically, the present invention relates to optical safety filtersthat provide laser protection across a plurality of narrowly selectedwavelength ranges corresponding to laser emissions, while also includinga color-balancing component that enhances the color renderingperformance of the filter.

In a number of commercial and military fields there is a growingawareness that certain wavelengths of energy emissions are harmful tothe eye. Generally, such energy emissions, in the form of a laseremission, are grouped at or around three wavelengths corresponding toapproximately 400-1400 nm. For example, energy emitted from a laseroperating in one of these wavelength ranges can cause both temporary andpermanent blindness and can be disorienting to those people that havebeen exposed. The adverse effects of energy emissions having wavelengthswithin these wavelength regions are only recently beginning to be fullyrecognized as applications that utilize such energy emissions are morefrequently employed. For example, there are a number of opticalcommunication protocols that utilize lasers tuned to these wavelengthsfor the transmission of data as well as a number of militaryapplications that employ infra-red and near infra-red laser energyemissions at these wavelengths in connection with the sighting ofweapons and target acquisition. As the environments in which the use ofsuch energy emissions increases, the potential for accidental exposureto such emissions also greatly increases.

In the past, to avoid accidental exposure to infra-red and visible laseremissions, people have attempted to protect their eyes through the useof nonselective filters that simply include a broad wavelength darkfilter that screens out the potential for exposure to harmful emissionlevels. In this regard, however, the broadband filters only reduced themagnitude of the exposure rather than screening out the harmfulwavelengths of energy. As a result, with only a few exceptions, suchfilters have generally been directed toward the reduction in intensityof the light transmitted, rather than to the filtering of any particularwavelength or group of wavelengths.

The problem with such a prior art approach is that the nonselectivereduction in overall light transitivity generally impacts the visualacuity of the wearer making the use of such filtering difficult if notimpossible to implement due to the severe limitations imposed on thevisibility of the wearer. One key area that further limits thewearability of such generalized filters is traffic signal recognition.To meet the standards required for use as sunglasses, the wearer must beable to differentiate between red and green traffic signals. Often broadfilters directed at screening the above laser energy emissions alsoresult in severely limiting the wearer's ability to differentiatebetween red and green objects making traffic identification difficult ifnot impossible.

Another prior art approach involved in laser filtering related to theuse of specialty lenses. The difficulty with such lenses is that theytypically have a limited range of properties, because they are made ofglass or high impact polymers such as polycarbonate, thereby requiringthat the additives used to modify the transmissivity must be compatiblewith the high temperatures required in making the glass or molding ofthe polymer material. The range of substances that are available thatare both compatible with the high molding temperatures and capable ofimparting the desired filtering properties is very narrow and generallydoes not provide the versatility typically encountered with organicdyestuffs that are normally utilized for narrow wavelength filtering. Anexample of such a prior art filter is illustrated in the performancegraph at FIG. 1. The curve illustrates a prior art optical filtertailored for filtering energy in the range of approximately 755 nm-1064nm. As can be seen, the filter provides a filtering performance curvethat exhibits filtering characteristics on the order of 5 opticaldensity (OD) between the wavelengths of about 755 nm to about 1064 nm.In addition, however, the filter still exhibits filtering on the orderof 4 OD for wavelengths as low as 700 nm and as high as 1080 nm. Sincetransmissivity is the inverse of OD to the base 10, this translates to atransmissivity of almost zero in the target filtering range of 755nm-1064 nm with a visible light transmission (VLT) across the remainingspectrum of only around 30-35%. As can be seen, the results indicate arelatively low performance filter with a limited VLT value.

Should the above approach be taken to create a filter to cover all threeof the identified energy emission ranges, a lens is produced thatexhibits a very undesirable muddy chartreuse green color. Not only isthis undesirable from a commercial standpoint, it further encounters theproblem that the filter does not allow the wearer to differentiate wellbetween reds and greens. Finally, such a lens has a low lighttransmissivity because the overlap of the three broad filtering rangesneeded to cover the target energy covers almost the entire visiblespectrum.

As a result there is a need for an optical filter that blocks narrowbands of energy emissions corresponding laser energy emission whilepreserving the wearer's ability to differentiate between reds andgreens. There is a further need for an optical filter that is moldedfrom a polymer and includes dyes that filter laser energy emissionswhile having a pleasing overall color and while also preserving thewear's ability to differentiate between colors.

BRIEF SUMMARY OF THE INVENTION

In this regard, the present invention provides for a molded opticalfilter that provides effective filtering of laser emissions whilepreserving the wearer's ability to differentiate and recognize colorsand providing a pleasing overall color as compared to the prior art. Thepresent invention is directed generally to a selective optical filterthat has multiple dyes therein to produce sharp notch filtering rangesat about blue, green, and infrared light spectrum and additional dyesfor color balancing to adjust the overall color of the filter making itmore pleasing and desirable to the wearer. In other words, the opticalfilter of the present invention effectively reduces transmission oflaser energy in the selected ranges while preserving the wearer'sability to differentiate colors and improving the overall color of thefilter itself thereby making the filter more desirable to the wearer.

It is therefore an object of the present invention to provide afiltering panel that filters laser energy emissions in the blue, green,red and infrared while also being suitable for use as sunglasses. It isa further object of the present invention to provide an optical filterthat filters laser energy emissions at about blue, green, red and IRwhile also including a color balance dye that improves the overall colorof the optical filter itself. It is still a further object of thepresent invention to provide a molded optical filter that includes dyesthat filter energy emissions to a non-hazardous level from laser whilealso including a color balance dye(s) to improve the overall color ofthe optical filter itself. These together with other objects of theinvention, along with various features of novelty that characterize theinvention, are pointed out with particularity in the claims annexedhereto and forming a part of this disclosure. For a better understandingof the invention, its operating advantages and the specific objectsattained by its uses, reference should be had to the accompanyingdescriptive matter in which there is described several embodiments ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings which illustrate the best mode presently contemplatedfor carrying out the present invention:

FIG. 1 is a graph depicting the filtering characteristics of a prior artoptical filter;

FIG. 2 is a graph depicting the filtering characteristics of a filterhaving three dyes covering the blue, green, red and IR wavelengths;

FIG. 3 is a graph depicting the filtering characteristics of a filter inaccordance with the teachings of the present invention;

FIG. 4 depicts a filter plate or window formed in accordance with theteachings of the present invention; and

FIG. 5 depicts a lens blank or eyewear formed in accordance with theteachings of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The best mode for carrying out the present invention is illustratedherein in the context of an optical filter that preferably includes dyesdirected at filtering energy emissions in and about the wavelengthranges of blue, green, red and IR and more particularly in the range oftraffic lights and lasers in the 530, 600-700 and military lasers whilealso including a color balancing dye(s) to improve the overallperformance and aesthetic appeal of the optical filter. As was statedabove, as applications that employ infrared and/or laser energyincrease, the need to protect people against accidental exposure alsogreatly increases. For this reason, the present invention provides anoptical filter capable of filtering energy emissions in the wavelengthranges that cover various laser energy emissions while also providing alens that is color balanced in a manner that preserves a wearer'sability to distinguish colors and has a more pleasing overall color ascompared to the prior art.

In the context of this invention, various optical terms are used todescribe the optical filter. To facilitate the understanding of theinvention, these terms are initially defined as follows:

Lens: an ophthalmic lens that provides refractive correction or a lensthat provides no refractive correction also known as a “plano lens”.

Visible light spectrum: energy emissions having a wavelength of betweenapproximately 400 nm and 780 nm.

Visible light transmission (VLT): the percentage of light in the visiblespectrum range that the filter of the present invention allows to passthrough to the eyes of the user.

Blocking: a measure of the percentage of light that is either reflectedby the surface or surface coatings or absorbed by the dye or plastic ofthe lens.

Substantially blocking: the point at which the filter of the presentinvention blocks over 99 percent of the incident radiation or transmitsless than one-percent (1.0%) of the incident radiation at each and everywavelength within the defined range.

Turning now to FIG. 2, an optical filter directed at filtering therelevant wavelengths. The optical filter can be seen to screen orsubstantially block all of the energy associated with emissions in theranges of approximately 190-530 nm, 700 nm through 1060 nm. As wasstated above however, such a filtering characteristic as is depicted inFIG. 2 has two distinct drawbacks in that it produces an optical filterhaving an unattractive color while also greatly impairing the wearer'sability to distinguish colors such as those in traffic signals. Toovercome this problem, the present invention includes dyes that provideselective screening of hazardous laser radiation and producecolor-balancing effects. The combination of these dyes has two effects.It provides protection from hazardous laser radiation while at the sametime providing glare protection and traffic color signal recognitionassociated with typically sunglasses.

As can be seen in FIG. 3, the present invention also provides for anoptical filter that includes dyes for selectively screening outhazardous laser radiation and color balancing dyes. The combination ofthese dyes allows you to be protected from laser radiation and alsoprotection glare protection while allowing you to see traffic signals.The optical filter of the present invention is intended to be formed asa polymer filter and may take the form of a filter panel, a lens blank,safety eyewear or a window. The optical filter is designed to beutilized in any environment where the potential for exposure to laserenergy emissions exists due to the fact that such energy emissions aredeleterious to the eyes. The optical filter of the present invention ispreferably formed from a transparent polymer matrix material that issuitable for making ophthalmic quality lenses. Preferably, the opticalfilter of the present invention is formed using a polycarbonate, nylonor acrylic. It is further preferred that the particular polymer selectedbe well suited to the application in which the finished optical filterwill be employed. For example, lens blanks 10 as are depicted in FIG. 4are typically formed using a polycarbonate while windows 20 as aredepicted in FIG. 5 are formed using acrylic.

In all cases, despite the application, the optical filter of the presentinvention provides an effective filter barrier to the targeted laserenergy emissions thereby preventing damage to the user's eyes whileproviding glare protection and traffic signal recognition. As can beseen in FIG. 3, dyes are incorporated into the lens material prior tothe molding of the lens. The dyes have characteristics that allow thelens to transmit a greater amount of the of the visible light spectrumadjacent the filtering ranges while blocking more than 99% of all energyemissions having wavelengths that fall in the of relevant hazardouslaser wavelengths ranges. This further allows color balancing to shiftthe overall color of the lens and allow the optical filter to meet thestandards required of sunglasses while not becoming too dark to bewidely usable.

In forming the optical filter of the present invention, two differentmethods may be employed. First, polymer molding feedstock in the form ofpolymer pellets is provided that is then mixed with the dye materialtypically in the form of a powder. The pellets and dye are mixed bytumbling the materials together. The pellet and dye mixture is thenintroduced into the feed hopper of an extrusion-molding machine whereinthe mixture is melted and homogenized in the barrel of the moldingmachine. Finally, the molten material is extruded either through anextrusion die or into a mold to form the finished optical filter.Alternately, in a second method, the molten material may be extrudedusing a small diameter extrusion die and pelletized to form ahomogenized, dyed polymer feed stock. These pellets are then utilized insubsequent molding operations wherein the pellets are remelted andfurther extruded or injected into a mold cavity to form the finishedoptical filter. The ability to mold the optical filter in accordancewith the teachings of the present invention provides a great advantageover prior art filters having the same filtering characteristics in thatthe prior art filters had to be formed and coated. Since the presentinvention optical filters can be molded, a large savings inmanufacturing time and cost is realized.

It can therefore be seen that the present invention provides a noveloptical filter having the ability to substantially block energyemissions from hazardous laser radiation, while preserving the abilityto distinguish between colors associated with traffic signals. For thesereasons, the instant invention is believed to represent a significantadvancement in the art, which has substantial commercial merit.

While there is shown and described herein certain specific structureembodying the invention, it will be manifest to those skilled in the artthat various modifications and rearrangements of the parts may be madewithout departing from the spirit and scope of the underlying inventiveconcept and that the same is not limited to the particular forms hereinshown and described except insofar as indicated by the scope of theappended claims.

1. An optical filter comprising: a transparent filter blank; a first dyedispersed within said filter blank, said first dye blocking greater than90 percent of energy emissions corresponding to a first wavelength; asecond dye dispersed within said filter blank, said second dye blockinggreater than 90 percent of energy emissions corresponding to a secondwavelength; a third dye dispersed within said filter blank, said thirddye blocking greater than 90 percent of energy emissions correspondingto a third wavelength; and a color balancing dye dispersed within saidfilter blank, said color balancing dye shifting a color of said filterblank containing said first second and third dyes from a green color toa brown color.
 2. The optical filter of claim 1, wherein saidtransparent filter blank is formed from a transparent polymer basematrix material.
 3. The optical filter of claim 2, wherein said polymerbase matrix material is selected from the group consisting of:polycarbonate, nylon and acrylic.
 4. The optical filter of claim 2,wherein said first, second, third and color balancing dyes are uniformlydispersed throughout said base polymer matrix material.
 5. The opticalfilter of claim 1, wherein said optical filter is selected from thegroup consisting of: lens blanks, lenses for eyewear, windows andfiltering plates.
 6. The optical filter of claim 1, wherein said first,second and third dyes are selected to have a filtering wavelength tofilter said first, second and third emissions yet preserve a wearer'sability to distinguish colors.
 7. The optical filter of claim 6, whereinsaid optical filter is a lens for sunglasses and said first, second andthird dyes are selected to preserve said wearer's ability to distinguishbetween red and green traffic signals.
 8. An optical filter comprising:a moldable transparent polymer base matrix material; a first sharpcut-on dye having an optical density of greater than 1 in a wavelengthrange of about 530 nm±20 nm dispersed within said base polymer matrix; asecond sharp cut-on dye having an optical density of greater than 1 in awavelength range of about 700 nm±20 nm dispersed within said basepolymer matrix; a third sharp cut-on dye having an optical density ofgreater than 1 in a wavelength range of about 1060 nm±20 nm dispersedwithin said base polymer matrix; and a color balancing dye dispersedwithin said base polymer matrix, said color balancing dye shifting acolor of said optical filter containing said first second and third dyesfrom a green color to a brown color.
 9. The optical filter of claim 8,wherein said polymer base matrix material is selected from the groupconsisting of: polycarbonate, nylon and acrylic.
 10. The optical filterof claim 8, wherein said first, second, third and color balancing dyesare uniformly dispersed throughout said base polymer matrix material.11. The optical filter of claim 8, wherein said optical filter isselected from the group consisting of: lens blanks, lenses for eyewear,windows and filtering plates.
 12. The optical filter of claim 8, whereinsaid first, second and third dyes are selected to preserve a wearer'sability to distinguish colors.
 13. The optical filter of claim 12,wherein said optical filter is a lens for sunglasses and said first,second and third dyes are selected to preserve said wearer's ability todistinguish between red and green traffic signals.